Desert Wind Rage's passive effect is that you deal 5 + Strength modifier damage to all enemies within 5 squares at the start of each of my turns. If I have the feat Deadly Rage (Player's Handbook 2) and/or the utility power Strength of Enduring Pain (Primal Power), will their increases to damage effect the Desert Wind Rage aura?

Effect: Until the end of your turn, you gain a bonus to damage rolls equal to the ongoing damage...

Both give a bonus to damage rolls. Desert Wind Rage's passive effect does not roll damage: 5 + Str is a static value. Thus, Desert Wind Rage's passive effect does not benefit from Deadly Rage or Strength of Enduring Pain (or almost any other damage boosters; pretty much all of them increase damage rolls).